The present invention relates generally to plunger covers and to plungers for use in syringes and to methods of fabrication of plunger covers and plungers for use in syringes, and particularly, to plunger covers and to plungers for use in syringes to inject fluids into a patient and to methods of fabrication thereof.
A number of injector-actuated syringes and powered injectors for use in medical procedures such as angiography, computed tomography, ultrasound and magnetic resonance imaging (MRI) have been developed. U.S. Pat. No. 4,006,736, the disclosure of which is incorporated herein by reference, for example, discloses an injector and syringe for injecting fluid into the vascular system of a human being or an animal. Typically, such injectors comprise drive members such as pistons that operatively connect to a syringe plunger. For example, U.S. Pat. No. 4,677,980, the disclosure of which is incorporated herein by reference, discloses an angiographic injector and syringe wherein the drive member of the injector can be connected to, or disconnected from, the syringe plunger at any point along the travel path of the plunger via a releasable mechanism. A front-loading syringe and injector system is also disclosed in U.S. Pat. No. 5,383,858, the disclosure of which is incorporated herein by reference. Front-loading syringes and syringe plungers for use therewith are also disclosed in U.S. Pat. Nos. 6,585,700 and 6,224,577, the disclosures of which are incorporated herein by reference.
Forward, sliding motion of the syringe plunger within the syringe barrel pressurizes the fluid within the syringe, and the pressurized fluid is injected into that patient via a syringe outlet. A common method of manufacturing syringe plungers adapted, for example, for use in connection with powered injectors is to place an elastomeric, sealing plunger cover over a rigid base. Such rubber covers can, for example, be manufactured by a vulcanization compression molding process. The rubber covers can, for example, be molded into a sheet and then manually hand cut (through a cutting die) from the sheet. Once cut, the rubber covers are, for example, washed in a silicone wash and then assembled onto a plunger base for insertion into a syringe. The process results in substantial material waste and can also result in substantial manufacturing costs and time.
U.S. Pat. No. 5,902,276, the disclosure of which in incorporated herein by reference, discloses a syringe plunger that is formed by a two-shot molding process. A hard plastic core is first formed in a first mold. Subsequently, the distal portion of the hard plastic core is overmolded with a soft rubber plunger cover in a second mold. The second overmolding can occur in the second mold while the core is still cooling to effect molecular bonding of the rubber of the cover with the as-yet uncured plastic of the core.
WO 2004/035289, the disclosure of which is incorporated herein by reference, a copy of which is included herewith and made a part hereof, discloses a method of manufacturing plungers for medical syringes wherein the plunger includes at least two parts. In that regard, the plunger includes a plunger body made of a first plastic and a piston body (in the form of a sealing cover) at the front of the plunger body made of a second plastic. The second plastic (an elastomer) is softer than the first plastic (a generally rigid plastic) of the plunger cover. In forming the plunger, the piston body is first formed by injection molding. Then, the plunger body (or a part thereof) is injected molded against or over the piston body.
Although a number of syringe plungers and methods of fabrication or manufacture of syringe plungers have been developed, it is desirable to develop improved syringe plungers and methods of fabrication of syringe plungers.